Hi, phoebecat3. Not a dumb question at all.
The First Friday and First Saturday devotions honor the Sacred Heart of Jesus and the Immaculate Heart of Mary, respectively. They were requested by Jesus and Mary in private revelations.
Jesus appeared to Saint Margaret Mary Alacoque, a French nun who lived in the 1600s, while she was at prayer. He revealed His Sacred Heart to her asked her to help establish devotion to His Sacred Heart, an infinite source of love, which we have wounded by our sins. He communicated twelve promises to her for people who consecrate themselves to His Sacred Heart and make reparation for the sins that wounded It. The last of these twelve promises established the First Friday devotion:
“The all-powerful love of My Heart will grant to all those who shall receive Communion on the First Friday of nine consecutive months the grace of final repentance; they shall not die under My displeasure, nor without receiving their Sacraments; My Heart shall be their assured refuge at that last hour.”
The First Saturday devotion was revealed by Mary to Lucia, one ot the three children to whom Our Lady had appeared at Fatima, Portugal in 1917. Years later (1925), after Lucia had become a nun, Mary appeared to her with this message:
“Have pity on the heart of your Most Holy Mother. It is covered with thorns with which ungrateful men pierce it at every moment, and there is no one to remove them with an act of reparation … My child, behold my heart surrounded with the thorns which ungrateful men place therein at every moment by their blasphemies and ingratitude. You at least try to console me. Announce in my name that I promise to assist at the hour of death with all the graces necessary for salvation, all those who, on the first Saturday of five consecutive months, go to Confession and receive Holy Communion, recite the Rosary, and keep me company for a quarter of an hour while meditating on the mysteries of the Rosary, with the intention of making reparation to me.”
These two devotions really go hand in hand, as the hearts of Jesus and Mary are united in perfect love. When Jesus’ heart was pierced by the soldier’s lance (John 19:33–37), Mary’s heart was pierced with sorrow, as Simeon had foretold:
Simeon blessed them and said to Mary his mother, “Behold, this child is destined for the fall and rise of many in Israel, and to be a sign that will be contradicted (and you yourself a sword will pierce) so that the thoughts of many hearts may be revealed.” (Luke 2:34–35)
When we sin, we offend both Jesus and His mother (who is also our mother by spiritual adoption). The First Friday and First Saturday devotions allow us to express, in the manner requested by Jesus and Mary, our sorrow for having wounded their hearts.